Rapid optimization of media stream bitrate

ABSTRACT

A data processing method comprises, using a media server during a first media session between a client device and the media server, determining a stable bitrate value for use as a rate of transmitting multimedia data from the client device to the media server; storing, in a database, the stable bitrate value for the client device in association with an identifier; receiving, from the client device, a request to establish a second media session; determining the identifier within the request; in response to the request, based on the identifier in the request, searching the database for the stable bitrate value that is associated with the identifier; in response to locating the stable bitrate value in the database, sending the stable bitrate value to the client device for use in estimating a bitrate for transmitting multimedia from the client device to the media server in the second media session; establishing, by the media server, the second media session, wherein the media server initially receives multimedia data from the client device at the stable bitrate.

TECHNICAL FIELD

The technical field of the present disclosure is computer hardware,software and computer systems for rapid optimization of media streambitrate during a multimedia session. The technical field of thedisclosure also is computer hardware, software and systems that areprogrammed for rapid optimization of media stream bitrate during amultimedia session.

BACKGROUND

The approaches described in this section could be pursued, but are notnecessarily approaches that have been previously conceived or pursued.Therefore, unless otherwise indicated herein, the approaches describedin this section are not prior art to the claims in this application andare not admitted to be prior art by inclusion in this section.

The popularity of multimedia sessions, such as media streams, isconstantly increasing as shown by the increasing use of videoconferences, video phone calls, streaming of live television, streamingof previously recorded events, Internet radio, and the like. Each ofthese services requires transferring a different amount of data betweenthe two or more parties involved in the multimedia session. Bitrate is ameasure of the number of bits that are conveyed or processed per unit oftime. Certain qualities of media require different bitrates. Some commonexamples, in approximate terms, are: telephone quality audio: 8kilobits/sec; Compact Disc quality audio: 1,400 kilobits/sec; 240 pvideo using the H.264 video compression standard: 400 kilobits/sec; 480p video using H.264: 1 megabit/sec; 720 p video using H.264: 2.5megabits/sec to 3.8 megabits/sec; 1080 p video using H.264: 4.5megabits/sec to 6.8 megabits/sec. H.264 is a popular video compressionstandard. 240 p, 480 p, 720 p, and 1080 p are common video resolutions,in which the p stands for progressive scan.

A given multimedia session may take place using varying bitrates based,for example, on a maximum stable speed that each device participating inthe multimedia session can maintain. As an example, consider a videostream that begins at 240 p and gradually increases to 1080 p over aperiod of time. Typically, when beginning a media session, all devicesthat connect to a given media server are treated the same, and thereforeall the multimedia sessions start at a default bitrate and increase overtime. However, not all devices, and their Internet connections, are thesame. Additional solutions are needed to improve the user experience.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 illustrates an example computer system in which the techniquesdescribed may be practiced, according to one embodiment.

FIG. 2 illustrates a programmable algorithm or method in accordance withan embodiment.

FIG. 3 illustrates an example implementation of rapid optimization ofmedia stream bitrate.

FIG. 4 illustrates a computer system upon which an embodiment may beimplemented.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however,that the present invention may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to avoid unnecessarily obscuring thepresent invention.

General Overview

Computer-implemented techniques are provided for rapid optimization ofmedia stream bitrates. Specifically, during a first media sessionbetween a client device and a media server, the media server determinesa stable bitrate for the client device. The stable bitrate may bedetermined using any suitable method at predetermined time intervalsduring the media session, continuously, or in any other manner. Thestable bitrate, along with an identifier for the client (such as anInternet Protocol (IP) address) is stored in a database. Additionalinformation may also be stored, such as an identifier for the mediaserver (such as an IP address), and/or a timestamp. The stable bitratemay be stored at any point during the media session, such as when themedia session ends, or when the connection has stabilized for apredetermined amount of time. Then, when the client device subsequentlyconnects for a second media session, the stable bitrate is retrievedfrom the database, and sent to the client device for use as the startingvalue in bitrate estimation. This greatly decreases the “ramp-up” timecommonly seen in bitrate estimation, and improves the user experience bybeginning with streaming media at the last stable bitrate for the givenclient and/or media server combination.

In some embodiments, a client device may both send and receive dataduring a media session, such as during a video or audio call orconference. Thus, there may be two separate bitrates involved in a mediasession: an upload or egress bitrate that measures the rate at which aclient can send data to a media server, and a download or ingressbitrate that measures the rate at which a client can receive data from amedia server. Due to Internet connections typically being asymmetric,the egress and ingress bitrates may be different. In the followingspecification, the stable bitrate refers to the upload rate at which aclient can send data to a media server.

A data processing method comprises, using a media server during a firstmedia session between a client device and the media server, determininga stable bitrate value for use as a rate of transmitting multimedia datafrom the client device to the media server; storing, in a database, thestable bitrate value for the client device in association with anidentifier; receiving, from the client device, a request to establish asecond media session; determining the identifier within the request; inresponse to the request, based on the identifier in the request,searching the database for the stable bitrate value that is associatedwith the identifier; in response to locating the stable bitrate value inthe database, sending the stable bitrate value to the client device foruse in estimating a bitrate for transmitting multimedia data between themedia server and the client device in the second media session;establishing, by the media server, the second media session at thestable bitrate.

Other embodiments, aspects and features will become apparent from thedisclosure as a whole.

Example Computer System Implementation

FIG. 1 illustrates an example computer system in which the techniquesdescribed may be practiced, according to one embodiment. In anembodiment, a computer system comprises components that are implementedat least partially by hardware at one or more computing devices, such asone or more hardware processors executing stored program instructionsstored in one or more memories for performing the functions that aredescribed herein. In other words, all functions described herein areintended to indicate operations that are performed using programming ina special-purpose computer or general-purpose computer, in variousembodiments. FIG. 1 illustrates only one of many possible arrangementsof components configured to execute the programming described herein.Other arrangements may include fewer or different components, and thedivision of work between the components may vary depending on thearrangement.

FIG. 1 illustrates a media server 105, a media application 110, adatabase 115, a signaling server 120, a client device 125, and a clientmedia application 130. Media server 105 may be any computing device,including but not limited to: server computers, work stations, personalcomputers, general purpose computers, laptops, wireless devices, wireddevices, portable or mobile devices, wearable computers, cellular ormobile phones, portable digital assistants (PDAs), smart phones,tablets, multi-processor systems, microprocessor-based or programmableconsumer electronics, game consoles, set-top boxes, network PCs,mini-computers, or network infrastructure devices including, but notlimited to, routers, switches, and other computing and/or infrastructuredevices.

Although a single media server 105 is depicted in FIG. 1, any number ofmedia servers, spanning one or more physical devices, may be used.Optionally, media server 105 may be located on the same physical deviceas database 115 and/or signaling server 120.

Media server 105 is communicatively connected to database 115, signalingserver 120, and/or client device 125 using any wired and/or wirelessconnection, such as any combination of a Local Area Network (LAN), aWide Area Network (WAN), an internetwork, the public Internet, or acompany network.

Media server 105 may serve any type of multimedia to any number ofclient devices. In one embodiment, media server 105 is configured toprovide video conferencing capabilities. Specifically, media server maybe a multipoint control unit (MCU) or a selective forwarding unit (SFU).MCUs receive and process audio and video data from clients and typicallymix the audio and video to create a single composite video. Thecomposite video is then streamed to the clients in a single mix. Whilethis solution enables relatively simple client software, the processingpower needed for the MCU is high, and the resulting presentation at theclient is generally inflexible. SFUs, in contrast, are more similar topacket data routers, as SFUs forward packets without media processing.

In one embodiment media server 105 executes the media application 110.While one media application 110 is shown for purposes of illustrating aclear example, other embodiments may execute multiple applications. Inan embodiment, the media application 110 is used for audio or videoconferencing, or any other type of media session. Additional instancesof media application 110, and/or different versions of media application(such as a client version), may optionally execute on client device 125to provide some of the functionality needed to implement this invention.

In one embodiment, media application 110 comprises program instructionsthat are programmed or configured to establish a media session andexchange media using the session. The media session may use, forexample, the Interactive Connectivity Establishment (ICE) (defined inRFC 5245), or any other method and/or standard. Media application 110may establish any number of media sessions simultaneously, such ashosting or participating in an audio or video conference with five, ten,or more client devices. A second instance of media application 110 mayalso execute on signaling server 120, as discussed below.

In one embodiment, media application 110 comprises program instructionsthat are programmed or configured to estimate available bandwidth anddetermine a stable bitrate for a media session. During a media session,media application 110 estimates available bandwidth periodically, suchas every minute or other suitable interval, although the frequency mayvary, such as based on the age of a media session. For example,estimation may occur more frequently at the start of a media session.The bandwidth may be estimated using any suitable method, such asdetecting anomalies (such as packet loss), or the lack thereof. Onemethod of bandwidth estimation and congestion control is described inthe second draft of the “A Google Congestion Control Algorithm forReal-Time Communication,” available from the Internet Engineering TaskForce (IETF) in the document “draft-alvestrand-rtcweb-congestion-02” inthe folder “html” of the domain toolsietf.org. The reader or user of thepresent disclosure is presumed to have read and understood the documentcited in the preceding sentence.

A stable bitrate value for a media session is a bitrate value for amedia session that has been consistently stable for a period of time. Inparticular, media application 110 determines a stable bitrate valuebased on satisfying the three following formulas, where R is equal tothe stable bitrate, BWE is the current bandwidth estimation, and C1, C2,and C3 are time periods:

1.) BWE>=R for the last C1 time;

2.) Actual Receiving Rate>=R for the last C2 time; and

3.) BWE has been non-decreasing for the last C3 time.

In the above formulas, C1, C2, and C3 may be any amount of time, such as20 seconds, 1 minute, or any other suitable amount. Further, C1, C2, andC3 may be the same or different amounts of time, may vary dynamically,and are individually configurable by a user, administrator, programmer,or other suitable entity. Alternatively, media application 110 maydetermine a stable bitrate by satisfying one of the above formulas, twoof the above formulas, or using any other standard for determining astable bitrate.

In one embodiment, media application 110 comprises program instructionsthat are programmed or configured to determine identifying informationfor the media session and store the stable bitrate and identifyinginformation for the media session. Media application 110 may determineidentifying information using any available method. Identifyinginformation may be any data that is able to identify a particular clientdevice, media server, or other device used in a media session. Inparticular, IP addresses for a particular media server and client deviceinvolved in a media session are identified.

Further, a timestamp may also be determined and included in theidentifying information. The timestamp indicates a time when the bitratewas determined to be stable and/or when the stable bitrate was stored inthe database. The stable bitrate and identifying information may bestored in a database in any suitable manner, by any component. Forexample, media application 110 may send the stable bitrate andidentifying information to a database management application (not shown)which subsequently stores the data in the database. The stable bitrateand identifying information may be stored in any order, such as(timestamp, client IP, server IP, stable bitrate). Alternatively, moreor less data may be stored.

In one embodiment, media application 110 comprises program instructionsthat are programmed or configured to search the database for a stablebitrate. In response to media application 110 receiving a request for anew media session, media application determines identifying informationfor the media session, such as a client IP address and a media server IPaddress, and uses this information to search database 115. Mediaapplication 110 may search database 115 by sending a request to adatabase management application to perform the search, and receiving theresults of the search, if any, in response. If the search of database115 is successful, a stable bitrate will be returned for the clientdevice. If the search of database 115 is unsuccessful, no stable bitratewill be identified, which may indicate that the client is a new clientdevice or that all previous records of a stable bitrate have expired.

Optionally, the search of database 115 may require that the timestampassociated with the bitrate is recent within a threshold amount of time.The threshold may be set by a user, administrator, programmer or othersuitable entity to any amount of time. For example, the threshold may be1 day, 10 days, 2 weeks, etc. Optionally, the threshold may be basedupon data, such as usage statistics or how frequently particular clientsconnect to a media server using different devices and/or Internetconnections, and may vary on a per client basis.

In one embodiment, information in database 115 may be matched usingexact matches or partial matches. An example of an exact match is whenthe client IP address and the media server IP address in the databaseexactly match the values for the new media session. An example of apartial match is when a network prefix matches the network prefix of theclient and/or media server for the new media session. A network prefixmatch would allow, for example, a client device to have a stable bitrateassociated with Server 1 even if the client device has only previouslyconnected with Server 2, provided that Server 1 and Server 2 are hostedon the same network. Network prefix matching may match at the/24 level,for example, or other bit levels or prefix lengths.

In one embodiment, media application 110 comprises program instructionsthat are programmed or configured to send and/or receive requests,messages, and/or data as needed to establish a media session andexchange media using the media session. The requests, messages, and/ordata may be sent in any format and in any manner. In particular, mediaapplication 110 sends the stable bitrate to the client device, and otherinformation needed to begin a media session, such as an IP address ofthe media server, in response to a request to establish a new mediasession.

In one embodiment, database 115 is any form of digital data storagerepository, such as a relational database, flat file, CSV file, simplenetwork management protocol (SNMP) management information base (MIB)object or other structured data structure, and may be stored on anysuitable storage device such as one or more hard disk drives, memories,or any other electronic digital data recording device configured tostore data. Although database 115 is depicted as a single element inFIG. 1, database 115 may span multiple devices located in one or morephysical locations. For example, database 115 may be one or nodeslocated at a data warehouse(s).

Additionally, in one embodiment, database 115 may be located on the samedevice(s) as media server 105 and/or signaling server 120.Alternatively, database 115 may be located on a separate device(s) frommedia server 105 and/or signaling server 120.

Database 115 is communicatively connected to media server 105 andsignaling server 120 using any wired and/or wireless connection, such asany combination of a LAN, a WAN, an internetwork, the Internet, or acompany network. In one embodiment, database 105 is a relationaldatabase, a columnar database, or any other type of database. Database105 may be of any size, portioned into any number of tables or otherunits, and may be organized in any suitable way. Database 105 stores andsearches data records, such as stable bitrates and identifyinginformation for media sessions.

In one embodiment, signaling server 120 is a signaling server used forestablishing media sessions between a particular media server and aparticular client device. Signaling server 115 may be any computingdevice, and may execute one or more applications, such as mediaapplication 110, to provide the functionality needed for the inventiondescribed herein. In particular, signaling server 115 includesfunctionality to initiate media sessions on behalf of media server and aclient device. Signaling server 115 may use any protocols such asSession Initiation Protocol (SIP) (described in RFC 3261), ExtensibleMessaging and Presence Protocol (XMPP) as described in RFC 6120, Jingleas described XMP-0166[0] and XEP-0176[1], and/or any other suitableprotocol to establish a media session.

As part of establishing a media session, signaling server 115 mayreceive requests from client devices, and determine an appropriate mediaserver with which to connect the client device. The determination may bebased on the load of the media servers, or the location of a particularmedia or data item the client wishes to access. An appropriate mediaserver in different instances may be one hosting an audio or videoconference. As part of establishing a media session, signaling server115 sends data to client devices, such as identifying data for a mediaserver with which to connect and/or a stable bitrate value. Identifyingdata for a media server may comprise an IP address and port number forthe media server, for example.

In one embodiment client device 125 may be any computing device,including but not limited to: work stations, personal computers, generalpurpose computers, laptops, Internet appliances, hand-held devices,wireless devices, wired devices, portable or mobile devices, wearablecomputers, cellular or mobile phones, portable digital assistants(PDAs), smart phones, tablets, multi-processor systems,microprocessor-based or programmable consumer electronics, gameconsoles, set-top boxes, network PCs, mini-computers, servers, racks,and the like. Although one client device 125 is shown in FIG. 1, anynumber of client devices may be present. Client device 125 iscommunicatively connected to media server 105 and signaling server 120through any kind of computer network using any combination of wired andwireless communication, including, but not limited to: a LAN, a WAN, theInternet, or a company network. Client device 125 may includeapplications, software, and other executable instructions to facilitatevarious aspects of embodiments described herein, such as client mediaapplication 130. Client media application 130 is programmed to supportvideo conferencing and/or audio conferencing. Client media application130 may be standalone or may be implemented through a web browser usingbrowser-executable code, and is a client version of media application110. Optionally, client media application 130 includes all of thefunctionality discussed above in regards to media application 110,and/or may be a separate instance of media application 110.

In one embodiment, client media application 130 comprises programinstructions that are programmed or configured to estimate bitrate andreceive a stable bitrate. Client media application 130 may estimatebitrate in any suitable manner. If client media application 130 receivesa stable bitrate, client media application uses the stable bitrate as astarting value in bitrate estimation when beginning a media session. Ifclient media application 130 does not receive a stable bitrate, thenclient media application 130 uses a default value as a starting value inbitrate estimation when beginning a media session.

Example Functional Implementation

FIG. 2 illustrates an example programmable algorithm or method for rapidoptimization of media stream bitrate. Although the steps in FIG. 2 areshown in an order, the steps of FIG. 2 may be performed in any order,and are not limited to the order shown in FIG. 2. Additionally, somesteps may be optional, may be performed multiple times, and/or may beperformed by different components. All steps, operations and functionsof a flow diagram that are described herein are intended to indicateoperations that are performed using programming in a special-purposecomputer or general-purpose computer, in various embodiments, at thesame level that is used by persons of ordinary skill in the art to whichthe disclosure pertains for communicating with one another about similarcomputer programs or algorithms. In other words, each flow diagram inthis disclosure is a guide, plan or specification of an algorithm forprogramming a computer to execute the functions that are described.

In step 200, a stable bitrate value is determined for a client. Asindicated by the dotted lines, step 200 and step 205 may be performedbefore step 210 occurs, during a media session prior to the new mediasession requested in step 210. Step 200 may occur any amount of time inadvance of step 210.

The stable bitrate value may be determined using the following formulas,as discussed above, where R is equal to the stable bitrate, BWE is thecurrent bandwidth estimation, and C1, C2, and C3 are time periods.

1.) BWE>=R for the last C1 time;

2.) Actual Receiving Rate>=R for the last C2 time; and

3.) BWE has been non-decreasing for the last C3 time.

In the formulas, C1, C2, and C3 may be any amount of time, such as 10seconds, 2 minutes, or any other suitable amount. Further, C1, C2, andC3 may be the same or different amounts of time, may vary dynamically,and are individually configurable by a user, administrator, programmer,or other suitable entity. Actual receiving rate refers to the actualrate at which packets and/or data is actual received in the mediasession. Alternatively, a stable bitrate may be determined by satisfyingone of the above formulas, two of the above formulas, or using any otherstandard. Specifically, the stable bitrate may be determined by a mediaserver.

In step 205, the stable bitrate value, client identifier, media serveridentifier, and/or timestamp are stored in a database in associationwith one another, for example, in column values in the same databaserecord. The stable bitrate value and any additional information may bestored in association with one another in any manner or order.Optionally, more or fewer data items may be stored. Multiple instancesor versions of a stable bitrate value for a given client may be stored,such multiple stable bitrates determined from different media sessions.As indicated by the dotted line, and discussed above, step 205 isperformed prior to step 210, in a separate media session prior to thenew media session discussed in step 210.

In step 210, a request for a new media session is received from aclient. The request may be received in any manner, and may be for anytype of media session, such as a video or audio conference, or othermedia stream. The request may be all or a portion of a payload in adigital data packet that is organized according to a media protocol ortransport protocol.

In step 215, an identifier for the client and/or the media server forthe new media session is determined. The identifier(s) may be determinedusing any suitable method. In one embodiment, the client identifier isextracted from data contained in the request, while the media server isselected based on factors such as load balancing and/or whether themedia server can access a specific resource (such as the media serverhosting a video or audio conference). For example, the client identifiermay be extracted from a header or payload of a request or inferred fromdata values that appear in a packet, message or other transmissionaccording to other protocols. The media server identifier is determinedafter a suitable media server has been identified for the request.

In step 220, a determination is made whether a stable bitrate value forthe client exists in the database. This determination is made based onthe results of a search of a database storing stable bitrates for clientdevices. A query, table lookup, or other form of search may be performedin the database, based on the identifier for the client. The search maybe performed in any manner, and a match may be based on an exact matchor a partial match. For example, if the identifiers used are IPaddresses, and the search requires an exact match, the client IP addressand the media server IP address need to match exactly to successfullylocate a stable bitrate value. Alternatively, a partial match may onlyrequire that a portion of the IP addresses match, such as the first 24bits of both the client IP address and the media server IP address,which may be termed a/24 match. Further, other restrictions may beplaced on successfully returning a stable bitrate, as discussed in step225. If there is not a stable bitrate for the client in the database,the method proceeds to step 240. If there is a stable bitrate for theclient in the database, the method proceeds to step 225.

In step 225, a determination is made whether the stable bitrate valuefound in the database is recent. A stable bitrate value is determined tobe recent if the timestamp associated with the entry in the database iswithin a threshold amount of time from a current time. The process maybe programmed to read the current time from a system clock, determine adifference between the system clock value and the timestamp, anddetermine whether the difference is less than or equal to a specifiedthreshold, which may be hard-coded or stored in a configuration file.For example, the threshold may be one week. Thus, if the stable bitratevalue obtained from the database is more than one week old, then thestable bitrate is not recent, and would not be used. However, if thestable bitrate was four days old, then the stable bitrate would bedetermined to be recent and available for use. The threshold may be setto any suitable amount by a user, administrator, programmer, or othersuitable entity, and may be changed dynamically based on any suitablefactors.

If the stable bitrate is not recent, then the method proceeds to step240. If the stable bitrate is recent, the method proceeds to step 230.

In step 230, the stable bitrate value is sent to the client device. Thestable bitrate may be sent to the client device in any format, and withany additional information. For example, a signaling server may send thestable bitrate and an IP address of the selected media server to theclient device so that the client device may subsequently connect to themedia server.

In step 235, the client device uses the stable bitrate value for bitrateestimation and establishes the media session. Specifically, the clientdevice uses the stable bitrate value in place of a default value forbeginning bitrate estimation. When the media session is established, theclient device will begin the media session initially sending data to themedia server at the stable bitrate value, rather than a lower defaultbitrate value. Thus, the media server begins the media session receivingdata at the stable bitrate. Therefore, a shorter amount of ramp up timewill be needed, if any. The media session may be established in anymanner.

In step 240, the client device uses a default bitrate value for bitrateestimation and establishes the media session. Specifically, the clientdevice uses a default value for the beginning of bitrate estimation. Thedefault value is a low value, and substantial ramp up time may berequired. The media session may be established in any manner.

Using this process, the optimization of bitrate values in transmissionof media streams is improved in client-server systems. Specifically,rather than using a standard default value, and waiting out the effectsof a bitrate ramp-up algorithm, a particular client device is able touse a proven, previously stable, bitrate value as the starting point inbitrate estimation. This greatly reduces the ramp-up period for mediasessions and can even completely remove the ramp-up when the storedstable bitrate is the same as the current stable bitrate for a givenmedia session. This results in more efficient use of network bandwidth,use of fewer CPU cycles that otherwise would be needed to executeinstructions of a ramp-up algorithm, and other technical benefits thatmay be evident from the disclosure as a whole.

Example Rapid Optimization of Media Stream Bitrate

FIG. 3 illustrates an example of rapid optimization of a media streambitrate in accordance with an embodiment.

In the embodiment of FIG. 3, database 300 has stored information from aprior media session. Specifically, database 300 stores data indicatingthat the stable bitrate is 1 Mbps, the timestamp is 12345, the client IPaddress is 192.168.0.1, and the media server IP address is 10.10.0.1.Signaling server 305 is a signaling server that communicates with clientdevices that want to establish new media sessions. Client device 310 isa computer with an IP address of 192.168.0.1, and media server 315 is aserver computer with an IP address of 10.10.0.1.

As an example, the client device 310 sends a media session request 320to signaling server 305.

In response to the request, signaling server 305 requests a stablebitrate from database 300 via request 325, and provides the clientdevice IP address (192.168.0.1) and the media server IP address(10.10.0.1) for use as search terms. After a search, database 300locates the stable bitrate of 1 Mbps in a record that associates one ormore of the client device IP address (192.168.0.1) and the media serverIP address (10.10.0.1) with the value (“1 Mbps”) and sends the stablebitrate to the signaling server in a result set at message 330.

The signaling server subsequently sends the media server IP address andthe stable bitrate to client device 310 at operation 335.

At operation 340, the client device 310 uses 1 Mbps stable bitrate asthe starting value for bitrate estimation, and the media server IPaddress to communicate with and establish a media session at 1 Mbps withmedia server 315.

Implementation Example—Hardware Overview

According to one embodiment, the techniques described herein areimplemented by one or more special-purpose computing devices. Thespecial-purpose computing devices may be hard-wired to perform thetechniques, or may include digital electronic devices such as one ormore application-specific integrated circuits (ASICs) or fieldprogrammable gate arrays (FPGAs) that are persistently programmed toperform the techniques, or may include one or more general purposehardware processors programmed to perform the techniques pursuant toprogram instructions in firmware, memory, other storage, or acombination. Such special-purpose computing devices may also combinecustom hard-wired logic, ASICs, or FPGAs with custom programming toaccomplish the techniques. The special-purpose computing devices may bedesktop computer systems, portable computer systems, handheld devices,networking devices or any other device that incorporates hard-wired andprogram logic to implement the techniques.

For example, FIG. 4 is a block diagram that illustrates a computersystem 400 upon which an embodiment of the invention may be implemented.Computer system 400 includes a bus 402 or other communication mechanismfor communicating information, and a hardware processor 404 coupled withbus 402 for processing information. Hardware processor 404 may be, forexample, a general purpose microprocessor.

Computer system 400 also includes a main memory 406, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 402for storing information and instructions to be executed by processor404. Main memory 406 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 404. Such instructions, when stored innon-transitory storage media accessible to processor 404, rendercomputer system 400 into a special-purpose machine that is customized toperform the operations specified in the instructions.

Computer system 400 further includes a read only memory (ROM) 408 orother static storage device coupled to bus 402 for storing staticinformation and instructions for processor 404. A storage device 410,such as a magnetic disk or optical disk, is provided and coupled to bus402 for storing information and instructions.

Computer system 400 may be coupled via bus 402 to a display 412, such asa cathode ray tube (CRT), for displaying information to a computer user.An input device 414, including alphanumeric and other keys, is coupledto bus 402 for communicating information and command selections toprocessor 404. Another type of user input device is cursor control 416,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 404 and forcontrolling cursor movement on display 412. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

Computer system 400 may implement the techniques described herein usingcustomized hard-wired logic, one or more ASICs or FPGAs, firmware andprogram logic which in combination with the computer system causes orprograms computer system 400 to be a special-purpose machine. Accordingto one embodiment, the techniques herein are performed by computersystem 400 in response to processor 404 executing one or more sequencesof one or more instructions contained in main memory 406. Suchinstructions may be read into main memory 406 from another storagemedium, such as storage device 410. Execution of the sequences ofinstructions contained in main memory 406 causes processor 404 toperform the process steps described herein. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “storage media” as used herein refers to any non-transitorymedia that store data and instructions that cause a machine to operationin a specific fashion. Such storage media may comprise non-volatilemedia and volatile media. Non-volatile media includes, for example,optical or magnetic disks, such as storage device 410. Volatile mediaincludes dynamic memory, such as main memory 406. Common forms ofstorage media include, for example, a floppy disk, a flexible disk, harddisk, solid state drive, magnetic tape, or any other magnetic datastorage medium, a CD-ROM, any other optical data storage medium, anyphysical medium with patterns of holes, a RAM, a PROM, and EPROM, aFLASH-EPROM, NVRAM, any other memory chip or cartridge.

Storage media is distinct from but may be used in conjunction withtransmission media. Transmission media participates in transferringinformation between storage media. For example, transmission mediaincludes coaxial cables, copper wire and fiber optics, including thewires that comprise bus 402. Transmission media can also take the formof acoustic or light waves, such as those generated during radio-waveand infra-red data communications.

Various forms of media may be involved in carrying one or more sequencesof one or more instructions to processor 404 for execution. For example,the instructions may initially be carried on a magnetic disk or solidstate drive of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 400 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 402. Bus 402 carries the data tomain memory 406, from which processor 404 retrieves and executes theinstructions. The instructions received by main memory 406 mayoptionally be stored on storage device 410 either before or afterexecution by processor 404.

Computer system 400 also includes a communication interface 418 coupledto bus 402. Communication interface 418 provides a two-way datacommunication coupling to a network link 420 that is connected to alocal network 422. For example, communication interface 418 may be anintegrated services digital network (ISDN) card, cable modem, satellitemodem, or a modem to provide a data communication connection to acorresponding type of telephone line. As another example, communicationinterface 418 may be a local area network (LAN) card to provide a datacommunication connection to a compatible LAN. Wireless links may also beimplemented. In any such implementation, communication interface 418sends and receives electrical, electromagnetic or optical signals thatcarry digital data streams representing various types of information.

Network link 420 typically provides data communication through one ormore networks to other data devices. For example, network link 420 mayprovide a connection through local network 422 to a host computer 424 orto data equipment operated by an Internet Service Provider (ISP) 426.ISP 426 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 428. Local network 422 and Internet 428 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 420and through communication interface 418, which carry the digital data toand from computer system 400, are example forms of transmission media.

Computer system 400 can send messages and receive data, includingprogram code, through the network(s), network link 420 and communicationinterface 418. In the Internet example, a server 430 might transmit arequested code for an application program through Internet 428, ISP 426,local network 422 and communication interface 418.

The received code may be executed by processor 404 as it is received,and stored in storage device 410, or other non-volatile storage forlater execution.

Extensions and Alternatives

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense. The sole and exclusive indicator of the scope of the invention,and what is intended by the applicants to be the scope of the invention,is the literal and equivalent scope of the set of claims that issue fromthis application, in the specific form in which such claims issue,including any subsequent correction.

What is claimed is:
 1. A method comprising: using a media server duringa first media session between a client device and the media server,determining a stable bitrate value based on an actual rate at which themedia server receives packets from the client device, the stable bitratefor use by the client device as an initial rate of transmittingmultimedia data from the client device to the media server; storing, ina database, the stable bitrate value for the client device inassociation with an identifier; receiving, from the client device, arequest to establish a second media session; determining the identifierwithin the request; in response to the request, based on the identifierin the request, searching the database for the stable bitrate value thatis associated with the identifier; in response to locating the stablebitrate value in the database and before receiving multimedia data fromthe client device, sending, by the media server, the stable bitratevalue to the client device, wherein the client device estimates aninitial bitrate for transmitting multimedia data from the client deviceto the media server in the second media session; establishing, by themedia server, the second media session; receiving, initially and by themedia server, multimedia data from the client device at the initialbitrate based on the stable bitrate.
 2. The method of claim 1, whereinthe media session is a video conferencing session.
 3. The method ofclaim 1, wherein the identifier comprises an Internet Protocol (IP)address of the client device.
 4. The method of claim 3, furthercomprising storing a media server IP address and a timestamp in thedatabase in association with the identifier and the stable bitratevalue.
 5. The method of claim 4, wherein searching the database furthercomprises using a prefix of the media server IP address as a search key.6. The method of claim 4, further comprising, in response to locatingthe stable bitrate value in the database, comparing the timestamp to acurrent time and determining that a difference of the timestamp and thecurrent time is within a threshold.
 7. The method of claim 1, whereindetermining the stable bitrate value comprises: determining, by themedia server, that a bandwidth estimation is equal to or greater thanthe stable bitrate value for a first time period; determining, by themedia server, that an actual receiving rate is equal to or greater thanthe stable bitrate for a second time period; determining, by the mediaserver, that the bandwidth estimation has not decreased for a third timeperiod.
 8. The method of claim 7, wherein the first time period, thesecond time period, and the third time period are 10 seconds.
 9. Acomputer system comprising: a media server comprising one or moreprocessors and electronic digital memory storing one or more sequencesof instructions which, when executed by the one or more processors,cause the one or more processors to perform: during a first mediasession with a client device, determining a stable bitrate value basedon an actual rate at which the media server receives packets from theclient device, the stable bitrate for use by the client device as aninitial rate of transmitting multimedia data from the client device tothe media server; storing, in a database, the stable bitrate value forthe client device in association with an identifier; establishing asecond media session; receiving multimedia data from the client deviceat an initial bitrate based on the stable bitrate; a signaling servercomprising one or more processors and electronic digital memory storingone or more sequences of instructions which, when executed by the one ormore processors, cause the one or more processors to perform: receiving,from the client device, a request to establish a second media session;determining the identifier within the request; in response to therequest, based on the identifier in the request, searching the databasefor the stable bitrate value that is associated with the identifier; inresponse to locating the stable bitrate value in the database and beforereceiving multimedia data from the client device, sending the stablebitrate value to the client device, wherein the client device estimatesthe initial bitrate for transmitting multimedia data from the clientdevice to the media server in the second media session.
 10. The systemof claim 9, wherein the media session is a video conferencing session.11. The system of claim 9, wherein the identifier comprises an InternetProtocol (IP) address of the client device.
 12. The system of claim 11,the instructions, when executed, further causing the one or moreprocessors to perform: storing a media server IP address and a timestampin the database in association with the identifier and the stablebitrate value.
 13. The system of claim 12, wherein searching thedatabase further comprises using a prefix of the media server IP addressas a search key.
 14. The system of claim 12, the instructions, whenexecuted, further causing the one or more processors to perform: inresponse to locating the stable bitrate value in the database, comparingthe timestamp to a current time and determining that a difference of thetimestamp and the current time is within a threshold.
 15. The system ofclaim 9, wherein determining the stable bitrate value comprises:determining, by the media server, that a bandwidth estimation is equalto or greater than the stable bitrate value for a first time period;determining, by the media server, that an actual receiving rate is equalto or greater than the stable bitrate for a second time period;determining, by the media server, that the bandwidth estimation has notdecreased for a third time period.
 16. The system of claim 15, whereinthe first time period, the second time period, and the third time periodare 10 seconds.